U0499 means a control module on the vehicle network has received a message from the Telematic Control Module that contains data outside an acceptable range or format. The telematics unit is transmitting, but the information it sends is being rejected as implausible by the receiving controller. This usually points to a fault within the telematic module, its power or network circuits, rather than the module that logged the code.
The module may generate and transmit out-of-range or garbled data due to an internal hardware defect or corrupted software calibration, causing receiving controllers to flag the message as invalid.
Low voltage, excessive voltage drop, or a poor ground can cause the module to behave erratically and broadcast serial data that other modules cannot validate.
Corrosion, pin damage, or high resistance in the communication bus circuits between the telematic module and other controllers can distort data packets enough to be read as invalid.
Non-factory devices improperly interfaced with the vehicle communication network can introduce electrical noise or alter message protocols.
In rare cases, the module logging the code may misinterpret an otherwise valid message because of its own network transceiver or software fault; this should only be considered after the telematic module and wiring are ruled out.
Yes. This code relates to data from the telematics system and typically does not affect engine control, braking, or steering. The vehicle is usually safe to operate, though connected services may not function.
No. Although the PCM may store this code because it detects the invalid data, the root cause is almost always the Telematic Control Module, its power supply, or network wiring. PCM failure is extremely unlikely.
Yes. Aftermarket electronics that are improperly connected to the vehicle’s communication network can corrupt data and trigger invalid data codes for the telematic module.
If the data fault was intermittent and communication returns to normal, the light may extinguish after several successful ignition cycles, but the stored code usually remains until it is cleared or the underlying fault is repaired.